Refrigerating apparatus



M y 1937. E. B. NEWlLL REFRIGERATING APPARATUS Original Filed Sept. 28, 1954 INVENTOR. I fan/4&0 B. New/1.4.

the

nnrnrcnna'rme arrn'rns Edward B. Newill, Dayton, Ohio,

General Motors Corporation, hayton, Ohio, a corporation of'lllelawarc assignor to Application September 28,1934, Serial No. M5355 Renewed July 7, 1936 a claims.

The present invention-relates to refrigerating systems and to evaporators for such systems.

The evaporator employed in the refrigerating system of the 'present invention and disclosed in the drawing comprising a part of the present application is similar in construction to the evaporator shown in the copending application of Herman J. Dick, Serial No. 661,201, filed on March 17, 1933. In

controls the ingress of liquid refrigerant to the evaporator, is not at all times responsive only to the level or amount of liquid refrigerant contained in the evaporator. Due to the location of the thermostat in evaporators of the type disr of liquid refrigerant in the type disclosed at a point closed and referred to, the thermostat will at times respond to the temperature of cold gaseous refrigerant in the evaporator instead of responding only to the temperature of the liquid refrigerant therein or to the amount of liquid refrigerant in contact with the thermostat and the level the evaporator will vary beyond desired limits thus impairing the cooling effect produced by the evaporator and also impairing the efiiciency of the refrigerating system connected to the evaporator. In other words the thermostat is usually located'in an evaporator of where there is very little temperature difference between the liquid refrigerant and the gaseous refrigerant contained in the evaporator thus necessitating very close or critical adjustment of the valve, to be actuated by the thermostat, for maintaining the level of liquid refrigerant in the evaporator between predetermined limits. Myinvention is therefore di Jrected to a refrigerating system wherein provisions are made to overcome the dimculties above enumerated by rendering the thermostat nonresponsive to the temperature of gaseous refrigerant in the evaporator and responsive only to the level of liquid refrigerant in the evaporator or to the amount thereof inintimate lieat exchange relation with the thermostat.

An object ofmy invention is to provide an improved refrigerating system and particularlya system employing an improved evaporator of the flooded type. v

Another object of my invention is to provide an improvedfiooded'evaporator fora refrigerating system,'wherein the level of liquid refrigerant is maintained between predetermined limits by means of a valve actuated-in'response to temperatures, the evaporator having all the advantages the use of evaporators of type disclosed and referred to it has been rator for a refrigerating system wherein the valve I which controls ingress of liquid refrigerant'to the evaporator is operated by a thermostat having a predetermined constant rate of heat supplied thereto in order to render the thermostat positive in its response to a variation in the level or amount of liquid refrigerant in the evaporator.

Further objects and advantages of the present invention will be apparent from the following description reference being had to the accompanying drawing wherein a preferred form of the present'inven tion will be clearly shown.

In the drawing:

' Fig. 1 discloses a diagrammatic showing of a closed refrigerating system having my invention incorporated therein; I

Fig, 2 is a front view of the evaporator employed in the refrigerating system shown in Fig.

1; and d Fig. 3 isan enlarged vertical sectional view of a portion ofthe evaporator showing an arrangement of the elements constituting my invention therein.

Referring to the drawing, for the purpose of illustrating my invention, the evaporator includes a pair of headers it and Ill shown as elongated cylinders disposed one above the other. The lower header it is provided with an inlet connection if for receiving liquid refrigerant. Up per header ii is provided with a gaseous refrigerant outlet connection it. The connection it includes an extension or stand-pipe it which extends to a point near the top of header it (see Fig. 3) and is for the purpose of preventing liquid refrigerant from flowing into thesuctlon line of the refrigerating system. A plurality of refrigerant conveying or distributing conduits it A are connected in parallel to the headers it and l i. These conduits may be of any desired form and are preferably of the form as disclosed. The conduits it extend laterally from vheader it thence upwardly and horizontally to header it. Each of these conduits may be constructed from a single length of tubing bent into the required form or they may be provided by two straight lengths of conduit connected by a U-shaped end connection as disclosed. A plurality of fins it of any desired shape or form are secured to and bridge the horizontally extending portions of conduits it to increase the heat absorbing capacity' of the evaporator. The particular shape and arrangement of the fins It forms no part of my invention. A tubular member I9 is sealed to the front wall of header I l and extends into the header and is closed. at its inner end to form a well for the reception of a thermostat bulb to be hereinafter more fully described.

- Referring to Fig. 1 the refrigerating system or the refrigerant liquefying and condensing unit operatively connected to the evaporator includes the customary compressor 25, condenser 26 and an expansion valve '21. The compressor is driven by a motor 28 under the control of a switch 29 actuated by expansion and contraction of a bellows 3| in response to pressures of refrigerant within the evaporator or within the low pressure portion of the system. Evaporated or gaseous refrigerant is withdrawn from the evaporator, by

the compressor, through the vapor-return conduit 32. The valve 21 may be of any conventional and well known construction and is adapted to be intermittently opened and closed to permit liquid refrigerant to flow from the condenser or receiver connected thereto to the evaporator of the reand 3). The expansion valve is normally adjusted to maintain the level of liquid refrigerant within the evaporator between predetermined limits;

As before stated the expansion valve 21' is adjusted and the thermostat for actuating same is ordinarily arranged to normally maintain the level of liquid refrigerant in the evaporator between certain predetermined limits. The thermostat bulb 35 is adapted to respond only to vari ations in the level of liquid refrigerant in the evaporator but as previously pointed out the location of the bulb 35 in evaporators of the type disclosed is such that the thermostat 35 will also respond, at certain times during operation of the system, to cold gaseous refrigerantin the evaporator. Without such provisions the thermostat 35 is not positive in its response to the liquid refrigerant level only in the evaporator and this level may vary beyond extreme limits thus destroying the desirable .characteristics sought to be obtained by the refrigerating system. This desirable characteristic being that of providing a flooded evaporator without the use of a floatvalve mechanism. Therefore this invention has to dowith the provision of a means for preventing the cold gaseous refrigerant from affecting or influencing the thermostat 35 so that the thermostat will be positive in responding to the level of liquid refrigerant only in the evaporator to thereby obviate the close adjustment of the expansion valve 21 relative to the thermostat. y

- I have found that if a small amount of artiflcal heat is supplied 'to the thermostat 35 at a predetermined constant rate the thermostat will be rendered responsive only to the liquid refrigerant level or to the amount of liquid refrigerant in contact withthe walls of the well lfl. Therefore I provide a well 38 in the thermostat bulb 35 and position a heater or an electric heating element 39 in the well 38. The heating element 39 is connected by wires 4] and 92 to the power lines leading to the switch 29 and motor 28 of the refrigerating system. As long as the main switch in the power line, leading to the refrigerating system,

-pletely submerge or is closed the heating element39 will be energized and a small amount of heat will be supplied to the thermostat bulb 35 at a constant predetermined rate.

The construction and adjustment of the valve I ciated therewithis such that liquid refrigerant preferably does not rise above the level shown in Fig. 3 of the drawing. The fluid content of thermostat bulb 35 is such that as long as liquid refrigerant in the header II is at a level to comto submerge the major portion of well l9 and consequently the bulb 35, located in the well l9, this bulb will not influence the valve 21 and valve 21 will remain closed to prevent liquid refrigerant from entering the evaporator. refrigeration'demands upon the evaporator the level of liquid refrigerant therein will fall below the norfnal high level thereof, shown in the drawing, and will expose the walls of well [9 and consequently thermostat 35 to gaseous refrigerant above the liquid refrigerant in the evaporator. Since the well [9 and thermostat bulb 35 located therein is normally submerged in liquid refrigerant and since the liquid refrigerant is capable of absorbing and carrying away the heat generated by the heater 39, by evaporation of the liquid refrigerant, the thermostat 35 is prevented from influencing or causing valve 21 to be actuated. By diminishing the amount of liquid refrigerant in contact with the well l9 and conse-' quently the bulb 35 located therein, and since the gaseous refrigerant is ineflicient or less capable than liquid refrigerant of absorbing and carrying away heat generated by the heater 39 this heat will act upon the fluid in the-thermostat bulb 35 to cause vaporization or expansion of the fluid thus rendering the bulb 35 effective foractuating the valve 21. Valve 21 is thereby opened in response to a change in the temperature of fluid in the thermostat 35 which is brought about by the lowered liquid refrigerant level and artificial heat supplied to the bulb 35 by the electric heater 39. The valve 21 upon being opened permits liquid refrigerant to flow from the liquid refrigerant supply line of the system. to the interior of the evaporator until the level of liquid refrigerant reaches a height sufllcient to completely submerge or to-submerge the major portion of the well. L9 and consequently thermostat 35 located in the well. After liquid refrigerant has attained its high level in the evaporator as described and as shown in the drawing the small amount of heat generated by the element 39will again be absorbed and carried away. by vaporization of the liquid refrigerant so as to permit the fluid content. of bulb 35 to condense therein or contract thus rendering the thermostat 35 ineffective for influ encing the valve 21. j

From the foregoing it can be determined that I have provided an improved refrigerating system and have provided an improved control for governing the flow of liquid refrigerant to the evaporator of the system. My invention renders the control, which admits liquid refrigerant to the evaporator of the system, positive in its response only to the level of liquid refrigerant or to the amount thereof, in the evaporator thus preventing the thermostat of the control system from being affected by gaseous refrigerant in the evaporator. A definite liquid refrigerant level, between certain predetermined limits, can be maintained in the evaporator of my improved system without However, if and when during certain the use of a float actuated valve mechanism and without danger of the level of liquid refrigerant rising to apoint in the evaporator where liquid refrigerant will be drawn into the suction line leading to the crankcase of the compressor of the system. My improved refrigerant flow control system also eliminates the necessity of closely adjusting the refrigerant expansion valve thus permitting the use of a more rugged and less expensive valve.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows: 1. A refrigerating system comprising in combination, an evaporator having a refrigerant inlet connection and a refrigerantoutlet connection,

- means for circulating liquid refrigerant to said evaporator, and means for supplying artificial heat to said portion of said last named means whereby said portion of said last named means is rendered responsive to a'variation in the level in thermal contact with refrigerant in said evaporator, and means for supplying artificial heat at a substantially constant rate to said portion of said last named means whereby said portion of said last named means is rendered responsive to a variation in the level of liquid refrigerant in the evaporator for actuating said refrigerant flow said evaporator and for withdrawing gaseous refrigerant therefrom, means for controlling the flow of refrigerant to said evaporator to maintain a quantity of liquid refrigerant therein, said last named means including a portion thereof disposed in thermal contact with refrigerant in said evaporator, and an electric heater for supplying heat to said portion of said last named means whereby said portion of said last named means is rendered responsive to a variation in the level of liquid refrigerant in the evaporator for actuating said refrigerant flow control means.

4. A refrigerating system comprising in combination, an evaporator having a refrigerant inlet connection and a refrigerant outlet connection, means for circulating liquid refrigerant to plying refrigerant to said evaporator and for withdrawing gaseous refrigerant'therefrom, means for controlling the flow of refrigerant to said evaporator to maintain a quantity of liquid refrigerant therein, said last named means including a portion thereof disposed in thermal contact with refrigerant in said evaporator, and an electric heater disposed in intimate thermal association with said portion of said last named means for supplying heatat a substantially constant predetermined rate thereto whereby said portion of said last named for actuating said refrigerant flow control means.

5. A refrigerating system comprising in combination an evaporator having a refrigerant inlet -connection and a refrigerant outlet connection,

means for circulating liquid refrigerant to said evaporator and for withdrawing gaseous refrigerant therefrom, a valve for controlling the flow of refrigerant to said evaporator to maintain a quantity of liquidrefrigerant therein, a thermostat disposed in thermal contact with refrigerant in said evaporator and operatively connected with said valve, and an electric heating element disposed in intimate thermal contact with said thermostat for supplying heat at a substantially constant predetermined rate thereto whereby said thermostat is rendered responsive to a variation in the level of liquid refrigerant in the evaporator for actuating said refrigerant flow control valve.

6. A refrigerating system comprising in combination, a cooling element, means for supsaid cooling element and for maintaining a substantial amount of refrigerant therein, said means including a portion disposed in thermal contact with refrigerant in said cooling element, and means for heating said portion of said means whereby said portion is rendered responsive to a variation in the amount of refrigerant in the cooling element for actuating said supply means.

7. A refrigerating system comprising in combination, acooling element, means for supplying a liquid refrigerating medium to said cooling element and for maintaining a substantial amount of the liquid refrigerant therein, said means including a portion disposed in thermal: I

contact with refrigerant in said cooling element, and means for supplying artificial heat to said portion of said means wherebysaid. portion of said means is rendered responsive to a variation in the level of liquid refrigerant in the cooling element for actuating said supply means.

8. A refrigerating system comprising in combination, a cooling element, a device for controlling between predetermined limits the temperature to be produced by said cooling element, said control device being located in heat transfer relation with said cooling element and directly exposed to the cooling effect produced thereby, means for at all times maintaining the temperature of said control device beyond the limits of temperature at which the cooling element is maintained, and said control device being operative in response to a varying rate of heat transfer between said cooling element and said control device.

- EDWARD B. NEWILL. 

